The present invention relates to methods and apparatus for detection of hydrogen halide and more particularly to the measurement of hydrogen chloride in trace amounts in a gas stream by chemiluminescent techniques.
Hydrogen chloride is identified as one of the trace constituents in both the upper and lower atmosphere. The identification has been done by various techniques such as theoretical modeling of the upper atmosphere, by solar radiometry, or collecting samples in the stratosphere and bringing them to the ground laboratory for analysis. This is extremely cumbersome and does not offer real time data required to construct better models of the atmospheric reactions. An additional problem is the concentration levels to be measured. The concentrations are suggested to be in the range of 10.sup.8 to 10.sup.9 molecules/cc which requires methods and apparatus capable of extremely sensitive measurements.
Chemiluminescent techniques possess the advantage of having a wide dynamic range and are useful for monitoring certain trace samples at the parts per billion level. Older chemiluminescent techniques had certain disadvantages. They required a very high vacuum, careful and precise control of the working pressure, and efficient light collection and collimating systems. In U.S. Pat. No. 3,692,485 to Neti and Bing, which is assigned to the same assignee as this application, there is described an improved method and apparatus for the chemiluminescent detection and measurement of nitric oxide which overcame these disadvantages of prior chemiluminescent techniques. The point source reaction chamber apparatus described in that patent has been incorporated into the present apparatus and makes the method of measurement of hydrogen chloride disclosed herein possible.